A SINGLE-STAGE, LIQUID-PHASE DIMETHYL ETHER SYNTHESIS PROCESS FROM SYNGAS III. DUAL CATALYST CRYSTAL GROWTH, DEACTIVATION, AND ACTIVITY CONSERVATION STUDIES

In the liquid phase dimethyl ether (DME) synthesis process, both the methanol synthesis catalyst )composed of CuO, ZnO, and Al₂O₃) and the methanol dehydration catalyst (composed of gamma-alumina) are slurried in the inert oil phase. Various long-term activity checks were conducted on these dual catalysts to characterize the crystal growth and the thermal aging behavior. X-ray powder diffraction, X-ray fluorescence and elemental intensity compositions, and the crystallite size distributions of the aged catalysts were examined. Based on the current investigation, it was established that the crystal growth and the catalyst deactivation problems in the methanol synthesis catalyst are less severe when it is used along with the methanol dehydration catalyst.     

Effect of Different Ratios of Si-Al of Zeolite HZSM-5 on the Activity of Bifunctional Catalysts Upon Dimethyl Ether Synthesis

Abstract

Four bifunctional catalysts were prepared by physical mixing of a commercial methanol synthesis catalyst (JC207 catalyst, a catalyst for methanol synthesis, which has been industrialized in China) with zeolite HZSM-5 (Si-Al ratios of 25, 38, 50, 150) as a methanol dehydration catalyst. The bifunctional catalyst (JC207/HZSM-5 [Si/Al = 38]) showed better performance, which can be attributed to more acidic sites with moderate strength of zeolite, and which can control methanol dehydration rate, which is a rate determining step.     

REGENERATION OF LIQUID PHASE METHANOL SYNTHESIS CATALYST

ABSTRACT

This work focuses on the influence of changes in catalyst structure on the catalytic activity in liquid phase methanol synthesis process. Long-term methanol production experiments were performed under various reaction environments in order to investigate the relationship between the catalytic activity and the crystallite size in the methanol synthesis catalyst. The regeneration experiments were also conducted in order to reduce the crystallite size of aged catalysts by inducing metallic phase redispersion. The experimental results showed that the drop in the catalytic activity was closely linked to the growth in the crystallite size in the catalyst. The crystallite size was reduced successfully by cyclic oxidation-reduction treatments and as a result the lost activity in aged catalysts was recovered.     

PHASES IN THE ACTIVE LIQUID PHASE METHANOL SYNTHESIS CATALYST

ABSTRACT

An attempt has been made to identify the phases present in the active catalyst for liquid phase methanol synthesis. X-ray powder diffraction was used to identify the phases. Only metallic Cu was detected, while no Cu species was found to be present. A significant amount of ZnCO₃ was found to be present in catalysts which had been subjected to high partial pressures of C0₂. This fact has hitherto not been reported in literature. Some speculations about the effect of ZnCO₃ on the life of the catalyst are made.     

CRYSTAL SIZE GROWTH IN THE LIQUID PHASE METHANOL SYNTHESIS CATALYST

ABSTRACT

The phenomenon of crystal growth in the methanol synthesis catalyst has been studied. Crystallite size distributions in the cuo/ZnO/Al₂O₃ methanol synthesis catalyst have been determined. The effects of temperature, reaction environment and time under reaction conditions have been studied. It is observed that water in the reaction mixture promotes crystal growth.     

The direct dimethyl ether (DME) synthesis process from syngas II. Intrinsic kinetics and catalyst deactivation in one-step LPDMEtm process

In Part I of this series, it was seen that the favorable thermodynamic and kinetic coupling in the one-step LPDME^tm process – of methanol dehydration reaction (very rapid kinetics and at/near thermodynamic equilibrium) with the methanol synthesis reaction (slower kinetics and under thermodynamic limitation) – leads the beneficial “chemical synergy”.

In this part II of Series, we briefly discern the intrinsic kinetics of the LPMeOH^tm and LPDME^tm systems, and also shed light of the catalyst deactivation phenomena in these processes. Among the many reports on intrinsic kinetics of the one-step LPMeOH^tm and LPDME^tm processes, two illustrative kinetic studies, from the groups of University of Akron and Air Products and Chemicals, Inc. are highlighted and discussed further. For development of intrinsic kinetic models of LPMeOH^tm and LPDME^tm systems, a detailed thermodynamic framework has been developed which allows one to compute the liquid phase concentrations of reactive species, at phase equilibria and at chemical reaction equilibria. The intrinsic kinetic models of the LPDME^tm system are mainly based on the independent, component kinetic models of methanol synthesis (van den Bussche and Froment, 1996) and methanol dehydration (Bercic & Levec, 1992). From an overarching analysis of the deactivation of supported copper catalysts for methanol synthesis and other reactions (methanol decomposition and methanol steam reforming), we propose that thermal sintering, i.e., increase in Cu particle size and loss of metal surface area, is the only cause of catalyst deactivation in methanol synthesis reactions over Cu/ZnO/Al₂O₃ industrial-type methanol catalysts.     

A SINGLE-STAGE,LIQUID-PHASE DIMETHYL ETHER SYNTHESIS PROCESS FROM SYNGAS I. DUAL CATALYTIC ACTIVITY AND PROCESS FEASIBILITY

ABSTRACT

A novel process for manufacturing dimethyl ether (DME) from CO-rich syngas in a single stage has been developed. This novel approach was based on the application of dual catalysis in the liquid phase process, in which two functionally different catalysts are slurried in the inert mineral oil. The experimental reaction rate studies for methanol and dimethyl ether synthesis were conducted in a three-phase, mechanically agitated slurry reactor. The effects of catalyst ratio, temperature, and pressure on the dual catalytic activity were studied. The experimental data bear additional significance because this is the first study of such kind to be conducted on the liquid phase methanol synthesis process.     

The direct dimethyl ether (DME) synthesis process from syngas I. Process feasibility and chemical synergy in one-step LPDMEtm process

A novel one-step process for co-production of dimethyl ether (DME) and methanol, in the liquid phase, was conceived as an advance over the liquid phase methanol synthesis process (LPMeOH^tm). This direct, one-step DME process (LPDME^tm) is based on the application of “dual catalysis”, where 2 functionally different yet compatible catalysts are used as a physical mixture, well-dispersed in the inert liquid phase. Three different reactions, methanol synthesis (via CO and CO₂), water-gas shift, and methanol dehydration (to form DME) take place over the 2 catalysts, Cu/ZnO/Al₂O₃ and typically γ-Al₂O₃. The thermodynamic and kinetic coupling of methanol dehydration reaction (very fast and at/near thermodynamic equilibrium) with the methanol synthesis reaction (slower kinetics and highly thermodynamic) leads to the observed “chemical synergy”. This synergy helps overcome the limitation on thermodynamic equilibrium conversion, and increases the per-pass syngas conversion and reactor productivity. The catalyst deactivation phenomena in LPDME^tm proess is also greatly alleviated compared to methanol alone; the increase in syngas conversion and methyl equivalent productivity (MEP) are sustained over a longer on-stream time.

Here, in this review, we survey the salient developments in the LPDME^tm process since its inception, first at UA research laboratories and elsewhere including Air Products and Chemicals, Inc. We demonstrate the rationale of the LPDME^tm process, and then outline briefly the research studies in the two processes, that illustrate the chemical synergy in the LPDME^tm process. This successful example of “cooperative catalysis” can be adapted in principle to many other organic reactions.     

浆态床合成二甲醚的研究

考察了合成甲醇催化剂和甲醇脱水催化剂对于浆态床合成二甲醚反应的影响。结果表明 ,甲醇合成催化剂对于CO转化率和二甲醚的选择性都有一定的影响。甲醇催化剂对于合成二甲醚反应的活性顺序为 :HY >γ Al2 O3 >Hβ >HZSM 5 ,反应结果结合NH3 TPD表征 ,认为甲醇脱水生成二甲醚的反应是以弱酸中心为活性中心 ,在强弱酸中心的协同作用下进行的     

Oxidative Dehydrogenation of Methanol on Chromium Oxide/Montmorillonite K10 Catalysts

Abstract

Methanol conversion was carried out on a mesoporous material—chromia/montmorillonite K10 (MK10)—in a pulse microcatalytic system. Methanol was converted to formaldehyde and ethylene by two different mechanisms. Methanol dehydrogenation increases by increasing reaction temperature (300–400°C) and as chromia loading decrease. On the other hand, the dehydration of methanol occurs at a higher temperature (400–500°C) and as chromia loading increase, 3–18% Cr. Redox and exposed nonredox Cr³⁺ are responsible for formaldehyde formation. There is a relationship between increased C₂H₄ production and the increase of Cr⁶⁺ phase according to the acidity of chromia catalysts 34 and 76 μL tert-Butylamine/g catalyst for 3% Cr and 18% Cr, respectively. Formaldehyde formation is diffusionally controlled at high temperatures (400–500°C) and kinetically controlled at a lower reaction temperature (300–400°C), while methanol dehydration to ethylene is surface reaction controlled at 400–500°C.     

ROLE OF IN-SITU PRODUCED METHANOL ON THE CATALYST DEACTIVATION IN THE LIQUID PHASE METHANOL SYNTHESIS PROCESS

ABSTRACT

The role of methanol produced in-situ in the liquid phase methanol synthesis process has been experimentally examined. The catalyst crystallite size is found to be more stable when the produced water and methanol are consistently removed from the catalyst active sites. The experimental evidence shows that in-situ produced water is not the only culprit for the catalyst crystallite size growth, rather, methanol is also responsible for contributing to crystallite growth and therefore catalyst deactivation

Hydrothermal leaching of the catalyst was also determined to be an active participant in catalyst deactivation. Two experimental designs were run to assess the influence of temperature, leaching solution concentration and pretreatment conditions on the extent of leaching of the methanol synthesis catalyst. Water and methanol were found to be active participants in the reduction of catalyst activity. Hence, the methanol/water solutions serve as potentially harmful agents in the leaching of aluminum and copper from the synthesis catalyst     

Sulfuration Pretreatment of Ni/Al2O3 Catalyst to Remove Butadiene in FCC C4 Fraction

Abstract

The Ni-based catalysts have more advantages than the most widely used Pd-based catalysts in selective hydrogenating of the butadiene in fluid catalytic cracking (FCC) C₄ fraction. But the selectivity and stability of the Ni-based catalysts aren't good. The sulfuration pretreatment is an effective process to improve the performance of the Ni/Al₂O₃ catalysts. The sulfuration conditions of the Ni/Al₂O₃ catalyst have been studied in this article. The results showed the fittest conditions are that the catalyst was in-situ presulfurized for 60 min by the solution of S concentration 0.07 mol/L. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis indicated that the presulfurization declined the Ni crystal dimension.     

CO_2加氢一步合成二甲醚催化剂的研究进展

针对CO2加氢一步合成二甲醚催化剂的活性载体、助剂、沉淀剂及沉淀次序、焙烧温度和制备方法等对中间产物甲醇合成的影响进行了综述,介绍了甲醇脱水催化剂组分的研究现状,并对催化剂的失活原因进行了分析,同时阐述了甲醇合成与甲醇脱水复合结构催化剂的研究趋势,最后提出了高效催化剂的研究开发思路。     

IN-SITU REDUCTION OF A METHANOL SYNTHESIS CATALYST IN A THREE-PHASE SLURRY REACTOR

ABSTRACT

A new method for the reduction of metal oxide catalysts has been developed, for the reduction of the CuO - ZnO - A1203 catalyst for liquid phase methanol synthesis. The reducing agent is a 5% hydrogen in nitrogen mixture and the operation is carried out at 446.09 KPa. This method makes it possible to reduce finely crushed catalyst (-100 + 120 mesh) in a three phase slurry reactor. This method offers several advantages over methods in which the catalyst is reduced in a gas-solid contact mode and then slurried for use. The catalyst has been shown to be very effectively reduced and reaches its full production capacity after reduction.     

The effect of physical and chemical treatment on nano-zeolite characterization and their performance in dimethyl ether preparation

Catalytic dehydration of methanol to dimethyl ether (DME) was investigated using physically and chemically modified H-Mordenite and H-Beta zeolites as catalysts. Physical modification was carried out using ultrasonic wave’s energy, while chemical modification was performed through impregnation in aluminum nitrate followed by calcination. The produced solid catalysts were evaluated as selective catalysts for the dehydration of methanol to dimethyl ether at 100–250 °C performed at three different contact times. Chemical and structural characterizations of the solid catalysts were identified using XRD, FT-IR, TEM, SEM and NH₃-TPD. Ultrasonication physical mixing of solids proved as useful tool of preparation, producing fine reordered crystals of nanocomposite zeolites with novel morphology. The newly ordered crystals were distinguished by their frame work structure, acidic properties, crystal and particle sizes, unit cell volume, pore opening, and favorable catalytic activity of 100% selectivity to DME at 200 °C for all contact times studied. The effects of Al₂O₃ on the dispersion and interaction within the nano-zeolite crystals and hence on the catalytic dehydration of methanol were verified as the major influence toward utmost selectivity.     

IN-SITU ACTIVATION OF METHANOL SYNTHESIS CATALYST IN A THREE-PHASE SLURRY REACTOR

ABSTRACT

In the liquid phase methanol synthesis process, syngas reacts in the presence.of fine catalyst particles slurried in the oil phase, in a three phase slurry reactor system. A method for activating high concentration ( ?25 wt. %) of the CuO-ZnO-Al₂O₃ catalyst in the catalyst-oil slurry has been successfully developed. This catalyst activation process can be of crucial significance in the research and development of the methanol synthesis process in a liquid entrained reactor.

The reducing gas contains 2% hydrogen in nitrogen mixture and this activation procedure is carried out at a pressure of 125 psi. The catalyst-oil slurry is subjected to a controlled temperature ramping from 110° to 250° C. The catalyst has beemshown to be effectively reduced after following this activation procedure, that is valid especially for high catalyst loadings in slurry. Since the reduction is carried out in the process liquid medium and inside the reactor system, the catalyst-oil slurry after the treatment is ready for the synthesis of methanol.     

铝盐加入方式对CuO/ZnO/Al_2O_3系催化剂性能的影响

用XRD,TD-DTG,TPR,N2吸附及N2O滴定法考察了铝盐的加入方式对CuO／znO／A12O3系催化剂前体及催化剂物相组成的影响;用加压微反评价装置考察了其对合成甲醇反应性能的影响。实验结果表明,铝盐的加入方式对催化剂前体物相组成及催化剂的反应活性有明显影响。Cu-Zn和Zn-Al分别沉淀有利于提高催化剂的低温活性;而Cu-Zn-Al三元共沉淀由于形成较多的类尖晶石相(Cu,Zn)Al2O4,降低了催化剂的低温反应活性,但提高了催化剂的热稳定性。保持催化剂中(Cu,Zn)Al2O4含量在适当水平对提高催化剂的整体性能至关重要。     

合成气一步法制二甲醚双功能催化剂的研究进展

概述了以合成气为原料一步法合成二甲醚双功能催化剂的研究现状及最新进展,分别介绍了双功能催化剂中的甲醇合成活性组分、甲醇脱水活性组分、两种活性组分的复合方法及配比等。锫和硼等是CuO-ZnO-Al2O3甲醇合成活性组分的良好助剂,硼、硅和钨可增强脱水组分γ-Al2O3的酸性,水蒸气处理和添加助剂可增加脱水组分HZSM-5的稳定性,共沉淀沉积法是制备双功能催化剂的较好方法。     

XPS STUDY OF IRON CATALYSTS FOR FISCHER-TROPSCH SYNTHESIS

ABSTRACT

The surface characteristics of Fe-Cu-K catalysts were determined by X-ray photoelectron spectroscopy (XPS). The surface composition of catalysis poisoned by carbonyl sulfide (COS) was investigated by XPS and compared widi the composition of unpoisoned catalyst. Sputtering with Ar⁺ ions was used to determine the elemental distribution of poisoned catalyst by COS as a function of depth from the surface. The results showed that the sulfur content decreased as die depth increased from the catalyst surface, while the iron content increased along the depth increased. FeS and FeS₂ were the main phases on the poisoned catalyst surface. Only a-Fe₂O₃ was found on oxide iron catalyst. Fej04 was the main phase of reduced catalyst treated in H₂CO ratio of 2.1.     

合成气一步法制二甲醚双功能催化剂中甲醇脱水组分对催化性能的影响

采用并流共沉淀法制备的甲醇合成CuO-ZnO-Al2O3催化剂与不同甲醇脱水组分混合制成合成气一步法制二甲醚双功能催化剂,并在高压固定床反应器评价其催化性能。发现以西南化工研究设计院自主研制的甲醇脱水制二甲醚催化剂(改性的γ-Al2O3)为脱水组分时表现出最佳的催化性能。NH3-TPD研究表明改性后的γ-Al2O3表面酸量和酸强度都有所增加,且在双功能催化剂表面同时存在着弱酸中心和中等强度的酸中心。